Auditory Temporal Processing in Adults with Hearing Impairment Related to Age and Traumatic Brain Injury

Difficulty understanding speech in noise is among the most common complaints in rehabilitative audiology. Treatment of such complaints is challenging, due in part to the wide variability among people with similar pure-tone thresholds. A series of studies are presented on speech recognition in listeners with various auditory impairments, including sensorineural hearing loss, age-related deficits in auditory processing, and traumatic brain injury (TBI). In the first study, high-rate amplitude modulation detection and rate discrimination were tested in older adults with sensorineural hearing loss, a population that is characterized by impaired temporal processing and an inability to use temporal cues in speech. The results of this study showed that high-rate envelope information is preserved in these individuals, suggesting that these cues may be utilized to improve speech recognition. Results from a listener with a history of TBI showed that variability among older adults may be related to acquired deficits in temporal processing. In the second and third studies, the role of temporal processing ability in complaints of difficulty understanding speech in noise following TBI was evaluated. Auditory complaints were evaluated using subjective and objective speech recognition tasks in people with a history of mild TBI and controls. Cognitive abilities were measured to determine a possible role of cognition in auditory impairments. The results suggest that listeners with auditory complaints after mild TBI have objective deficits in temporal processing and speech recognition in noise, despite normal pure-tone thresholds and cognition. These data are consistent with long-term physiological damage to the auditory system after mild TBI, and provide new insights into the diagnosis and rehabilitation of neurosensory deficits in this population. Together, the findings presented here provide evidence supporting the role of temporal processing ability in speech recognition in noise, and suggest that hearing loss rehabilitation can be improved by addressing temporal processing deficits in impaired populations.